Consolidated Statements of Comprehensive Income (Loss) - USD ($) $ in Thousands	12 Months Ended
	Dec. 31, 2019	Dec. 31, 2018	Dec. 31, 2017
Net income (loss)	$ (12,348)	$ (30,770)	$ 29,993
Available-for-sale investments
Net change in unrealized gain (loss) on available-for-sale investments	9	14	(15)
Less: Reclassification adjustment for net losses (gains) on investments recognized during the year		9	(5)
Net change in unrealized gain (loss) on available-for-sale investments	9	23	(20)
Other comprehensive income (loss), net of tax	9	23	(20)
Comprehensive income (loss)	$ (12,339)	$ (30,747)	$ 29,973